1. Field of the Invention
This invention relates to a grommet with an excellent waterproof ability used, for example, when a wire harness (i.e., a bundle of wires) for an automobile is passed through a panel.
2. Description of the Related Art
One known grommet of the type described is shown in FIGS. 7(a) to 7(c) and 8(a) to 8(d). As shown in FIGS. 7(a) to 7(c) and 8(a) to 8(d), this grommet 1 is integrally molded of a rubber material (soft elastic material), and includes a cylindrical wire fitting portion 2 for fitting on and holding a wire harness W passing therethrough, and a panel fitting portion 4 of a substantially oval tubular shape for being compressively elastically deformed to be fitted in a through-hole 9 of an oval shape formed through a panel 8. Straight portions (designated by P in FIG. 9) of the panel fitting portion 4 are equal in thickness to arcuate portions (designated by Q in FIG. 9) thereof. Namely, the panel fitting portion 4 is formed integrally with the wire fitting portion 2 through a wall portion 3 of a substantially oval disk shape, and has a slanting guide portion 5 to be guided to the through-hole 9 in the panel 8, a fitting groove 6 to be fitted in the through-hole 9, and an abutment flange portion 7 to be abutted against that portion of the panel 8 around the through-hole 9. The thickness of the straight portions P of the slanting guide portion 5 at its distal end 5a is equal to the thickness of the arcuate portions Q at the distal end 5a (that is, they have the same thickness L between the bottom surface of the fitting groove 6 and the distal end 5a as shown in FIGS. 7(b) and 7(c)). Also, the thickness (designated by M in FIG. 7(c)) of the straight portions P of the abutment flange portion 7 is equal to the thickness (designated by M in FIG. 7(b)) of the arcuate portions Q thereof. Techniques analogous to the above grommet 1 are disclosed in Japanese Utility Model Unexamined Publication No. Hei. 5-47675 and Japanese Patent Unexamined Publication Nos. Hei. 7-296661 and Hei. 7-282666.
In the above conventional grommet 1, however, when fitting the fitting groove 6 of the panel fitting portion 4 in the through-hole 9 in the panel 8, there are exerted forces G which urge the arcuate portions Q of the panel fitting portion 4 inwardly as shown in FIG. 9, so that the straight portions P of the panel fitting portion 4 and straight portions of a lip-like seal portion 6a of the fitting groove 6 are much deformed inwardly as shown in FIGS. 8(a), 8(c), 9 and 10(c), and as a result the pressure of contact of the panel fitting portion 4 of the grommet 1 with the through-hole 9 in the panel 8 is reduced, and when an external load, such as a twisting force, is applied to the wire harness W, it is possible that a gap is formed between the panel fitting portion 4 of the grommet 1 and the through-hole 9 in the panel 8, and water or the like may intrude through this gap.